Lead-free perovskite materials have gained significant attention for piezoelectric applications due to environmental concerns. In recent years, regulatory bodies like RoHS and WEEE have further boosted the demand for eco-friendly technologies. This chapter offers a concise overview of the design strategies and structure-property relationships of major lead-free systems, including (K,Na)NbO3 (KNN), (Bi0.5Na0.5)TiO3-BaTiO3 (BNT-BT), and Ba(Zr,Ti)O3-(Ba,Ca)TiO3 (BZT-BCT). Their applications are also highlighted, emphasizing these materials as viable alternatives to hazardous lead-based compounds such as Pb(Zr,Ti)O3 (PZT). Key design approaches like compositional engineering, domain tuning, and advanced processing techniques, particularly spark plasma sintering and templated grain growth have been shown to greatly improve electromechanical performance. The origins of excellent electromechanical properties are further examined through intrinsic and extrinsic mechanisms. Special focus is given to morphotropic and polymorphic phase boundary effects, similar to those seen in PZT. The chapter ends with a discussion of how these materials are integrated into real-world applications, including sensors, actuators, energy harvesters, and biomedical devices. Lead-free piezoelectrics, thanks to their unique performance benefits, offer promising pathways toward next-generation smart, wearable, and environmentally sustainable technologies.